RE: BLE Mesh questions

Mitch996 — Mon, 31 Jul 2017 02:50:56 GMT

Loud and clear! Thank you Bjørn, I have no more question as of now! Thank you!

RE: BLE Mesh questions

bjorn-spockeli — Wed, 26 Jul 2017 10:46:23 GMT

Hi Mitch,

A1: The most sensible approach is to have a dedicated provisioner in form of a PC or phone/tablet application. The provisioner needs to keep information about the entire network, and this is not needed for each node. Nodes in the network normally operates only as provisionees before the become nodes.

A2: The latency will largely depend on number of hops between source and destination, and the advertising interval. Some time for processing in the node, and possibility of queuing in the node must be accounted for, which should be less than 2 ms.

Worst case: (2ms + Advertising_Interval) * no_of_hop, assuming no packet loss.

Still assuming no packet loss, but averaging out on the wait time to advertise will give: (2ms + Advertising_Interval)/2 * no_of_hop.

A3: Each device that is provisioned into the mesh by a provisioner will only stores a range of addresses, a network key, and a device key. It is only the provisioner that has access to the full list of devices in the network and their addresses.

A4: No, the Nordic BLE Mesh is a flooding mesh, i.e. a broadcast-based network protocol, where every device in the network sends and receives all messages to and from all devices within radio range. This is in accordance with the Bluetooth Mesh Specification, found here. Adding routing is possible, but it will then be considered a proprietary feature.

The flooding based approach to message relaying can cause a lot of redundant traffic on air, which may impact the throughput and reliability of the network. While all devices in a network may act as relays, it is highly recommended to limit the number of relays to restrict this effect. The rate of relay-enabled devices in the network is a trade-off between message route-redundancy and reliability. It should be tuned according to network density, traffic volumes, network layout, and requirements to reliability and responsiveness.

Best regards

Bjørn